1. Field of the Invention
The present invention relates to a display control device of a liquid crystal panel for controlling display data to be displayed on the liquid crystal panel, and a liquid crystal display device.
2. Description of the Related Art
Liquid crystal display devices are low in power consumption and compact in size, and thus are widely adopted in personal computers, television sets, and so on. In a liquid crystal display device, an electric field applied to each liquid crystal cell (pixel) of the liquid crystal panel is adjusted to change the transmittance of the liquid crystal cell for image display. Liquid crystal cells vary in transmittance relatively slowly. Consequently, in displaying moving images in particular, blurs in which data of previous frames appears overlapped (image trails) tend to occur. This phenomenon is unique to liquid crystal display devices, not seen in CRTs (Cathode Ray Tubes).
To reduce trails and bring the moving image display performance close to that of CRTs, there has been developed a technology called an impulse drive system which imitates the waveforms of applied voltages in CRTs. In addition, even in the case of a conventional hold drive system, techniques named as an overdrive method and an overshoot method have been developed for the sake of improved moving image display performance. Here, the hold drive system refers to a technology in which signals corresponding to the same image data are output to the liquid crystal cells over a period of one frame.
An overview of the overdrive method and overshoot method has been disclosed, for example, in FIG. 3 of Japanese Unexamined Patent Application Publication No. 2001-125067. The overdrive method is a technique for writing more emphasized data signals than the data signals corresponding to pixel data for actual display, to the liquid crystal cells (overdrive) so that the liquid crystal cells reach their target values in transmittance within a single frame period. The overshoot system is a technique for emphasizing the data signals further so that the liquid crystal cells change in transmittance to exceed their target values within a single frame period (overshoot), and for restoring the transmittances to the target values in the next one frame period.
In the foregoing overshoot method, greater emphasis on the data signals accelerate the changes of transmittance (pixel response) with an improvement in the moving image display performance. The more the data signals are emphasized, however, the greater the differences between the target transmittances corresponding to the input image data and the emphasized transmittances become. This results in a higher propensity to new trails, sometimes deteriorating the appearance of so-called moving image display. The trails resulting from overshoot occur depending on the display pattern. That is, when the overshoot method is employed, it is impossible to enhance the appearance of moving image display in all display patterns.